Yeah, you're right, they're related to WinUI. But what I meant is that such features aren't inherently expensive, they're just made expensive due to the choice of UI framework.
Display scaling is very fast in GDI apps and has no impact on launch time, a tab bar is essentially just an array of buttons (minimal impact on launch time?) and transparency is a virtually cost-free feature coming from DWM. I wrote a WinUI lookalike using its underlying technology (Direct2D and DirectComposition) directly one time and that results in an application that starts up within ~10ms of CPU time on my laptop, quite unlike the 450ms I'm seeing for WinUI. That is including UIA, localization and auto-layout support.
Display scaling is very fast in GDI apps and has no impact on launch time, a tab bar is essentially just an array of buttons (minimal impact on launch time?) and transparency is a virtually cost-free feature coming from DWM. I wrote a WinUI lookalike using its underlying technology (Direct2D and DirectComposition) directly one time and that results in an application that starts up within ~10ms of CPU time on my laptop, quite unlike the 450ms I'm seeing for WinUI. That is including UIA, localization and auto-layout support.